Not applicable
1. Field of the Invention
The present invention relates to pollution abatement. More particularly, the present invention relates to abatement of organic pollutants.
2. General Background of the Invention
A wide range of technologies is currently available for degradation of pollutants, including chemical and biological techniques. Many of these methods, however, are limited by the presence of non-pollutant compounds (matrix). The matrix can sequester the pollutant away from biologically or chemically active sites. Furthermore, the matrix can scavenge reactive transients in chemical systems, thereby lowering degradation efficiency. Biological systems are often limited by toxic effects, especially when high pollutant concentrations or mixtures are present.
The use of iron(II) and hydrogen peroxide alone is severely limited by matrix species through: 1) sequestration of pollutants away from the bulk aqueous phase, 2) chelation of iron(II) into sites that are physically separate (on a molecular scale) from the location of pollutants, and 3) scavenging of hydroxyl radical by matrix compounds.
Current methods for soil washing involve the use of surfactants or cyclodextrins. These methods exhibit some success in washing organic pollutants from soils or aqueous solutions, but they do not degrade the pollutant. Additional further treatment of the waste is still necessary after its removal from the contaminated site. The second treatment step adds additional costs, makes these methods more complicated, and limits their applicability to in situ remediation.
The following U.S. Patents are incorporated herein by reference: U.S. Pat. Nos.: 6,046,375; 5,967,230; 5,919,982; 5,755,977; 5,741,427; 5,520,483; 5,716,528; 5,585,515; 5,425,881; and 5,190,663.
U.S. Pat. No. 5,425,881 discloses a method for the extraction of an organic pollutant from contaminated soil without further contaminating the soil with organic solvents comprising the step of mixing aqueous solutions of cyclodextrins, or cyclodextrin derivatives selected from the group consisting of alkyl, hydroxyalkyl and acyl substituted cyclodextrin derivatives or cross-linked cyclodextrin polymers or cross-linked cyclodextrin derivatives selected from the group consisting of alkyl, hydroxyalkyl and acyl substituted cyclodextrin derivatives, with the contaminated soil.
U.S. Pat. No. 5,190,663 discloses a process for removing dissolved polynuclear aromatic hydrocarbons from an aqueous composition which comprises the step of contacting said composition with a water insoluble inclusion agent comprising an anchored cyclodextrin, said cyclodextrin having an inclusion cavity diameter of at least about 10 angstroms, wherein the concentration of dissolved organics in said aqueous composition is no greater than about fifteen percent by weight.
U.S. Pat. No. 5,741,427 describes the use of Fenton""s reagent for soil remediation. This patent utilizes iron complexing agents to limit the reactivity of H2O2 with iron to allow more substantial subsurface penetration of the reagents before they are consumed. However, the patent does not utilize simultaneous binding of iron and the pollutant, and it does not indicate the use of cyclodextrins.
Commercial applications of Fenton chemistry to remediation of contaminated soil are currently in use. These methods add both iron and peroxide to the saturated zone, and utilize iron chelators and peroxide stabilizers (Greenberg et al., 1997; Watts and Dilly, 1996). Such applications have been successful in remediating the saturated zone after petroleum leakage from an underground storage tank. However, conditions for such remediation have typically been developed from empirical observations of degradation efficiency rather than from a fundamental understanding of the HO. dynamics. Furthermore, a large excess of peroxide is often used. Indeed, Jerome et al. (1997, 1998) concluded that excess peroxide was one of two top cost items in their remediation process at the Savannah River Site, and they concluded that the proportionate peroxide costs would increase with increasing scale of the problem.
In situ remediation techniques based on the use of Fenton""s reaction (EPA, 1996; EPA, 2000; Geo-cleanse, 2000) have been found to be inefficient in many soils owing to the high reactivity of the reagents with soil constituents (Jerome et al., 1997; Li et al., 1998; Wang and Brusseau, 1998; Lindsey and Tarr, 2000).
The following references are incorporated herein by reference:
EPA, National Center for Environmental Research, http://es.epa.gov/ncerqa_abstracts/centers/hsrc/detection/det9.html, 1996.
EPA, Urban Watershed Management Branch, http://www.epa.gov/ednnrmrl/projects/urban/fenton.htm Geo-Cleanse, Inc., www.geocleanse.com, 2000.
Jerome, K. M., B. Riha, and B. B. Looney, xe2x80x9cFinal Report for Demonstration of In Situ Oxidation of DNAPL Using the Geo-Cleanse Technology,xe2x80x9d WSRC-TR-97-00283, Westinghouse Savannah River Company, 1997.
Li, Z. M., P. J. Shea, and S. D. Comfort, xe2x80x9cNitrotoluene destruction by UV-catalyzed Fenton oxidation,xe2x80x9d Chemosphere 36 (8) 1849-1865, 1998.
Wang, X. and M. L. Brusseau, xe2x80x9cEffect of pyrophosphate on the dechlorination of tetrachloroethene by the Fenton reaction,xe2x80x9d Env. Toxicol. Chem. 17 1689-1694, 1998.
Lindsey, M. E. and M. A. Tarr, xe2x80x9cInhibition of Hydroxyl Radical Reaction with Aromatics by Dissolved Organic Matter,xe2x80x9d Environ. Sci. Technol. 34, 444-449, 2000.
Greenberg, R. S., T. Andrews, P. K. C. Karala, and R. J. Watts, xe2x80x9cIn-Situ Fenton-Like Oxidation of Volatile Organics: Laboratory, Pilot and Full-Scale Demonstrations.xe2x80x9d Presented at Emerging Technologies in Hazardous Waste Management IX. Pittsburgh, Pa., 1997.
Watts, R. J., and S. E. Dilly, xe2x80x9cEvaluation of iron catalysts for the Fenton-like remediation of diesel-contaminated soils,xe2x80x9d J. Haz. Mat. 51, 209-224, 1996.
Jerome, K. M., B. B. Looney, and B. Riha, xe2x80x9cField Demonstration in Situ Fenton""s Destruction of DNAPLs,xe2x80x9d WSRC-RP-98-0001 1, Westinghouse Savannah River Company, 1998.
Watts, R. J., M. D Udell, P. A. Rauch, S. W. Leung, xe2x80x9cTreatment of Pentachlorophenol-Contaminated Soils Using Fenton""s Reagent,xe2x80x9d Haz. Waste Haz. Mat. 7(4), 335-345, 1990.
Watts, R. J., S. Kong, M. Dippre, W. T. Barnes, xe2x80x9cOxidation of Sorbed Hexachlorobenzene in Soils Using Catalyzed Hydrogen Peroxide,xe2x80x9d J. Haz. Mat. 39 33-47, 1994.
Lipczynska-Kochany, E., G. Sprah, S. Harms, xe2x80x9cInfluence of Some Groundwater and Surface Waters Constituents on the Degradation of 4-chlorophenol by the Fenton Reaction,xe2x80x9d Chemosphere 30, 9-20, 1995.
Gau, S. H., F. S. Chang, xe2x80x9cImproved Fenton Method to Remove Recalcitrant Organics in Landfill Leachate,xe2x80x9d Water Sci. Tech., 34, 455-462, 1996.
Kim, Y. K., I. R. Huh, xe2x80x9cEnhancing Biological Treatability of Landfill Leachate by Chemical Oxidation,xe2x80x9d Environ. Eng. Sci. 14(1), 73-79, 1997.
Walling, C. xe2x80x9cFenton""s Reagent Revisited,xe2x80x9d Acc. Chem. Res. 8, 125-131, 1975.
Haber, F., J. Weiss, xe2x80x9cThe Catalytic Decomposition of Hydrogen Peroxide by Iron Salts,xe2x80x9d Proc. Roy. Soc. A 147, 334-351, 1934.
Halliwell, B., J. M. C. Gutteridge, xe2x80x9cFormation of Thiobarbituric-acid-reactive Substance from Deoxyribose in the Presence of Iron Salts: The Role of Superoxide and Hydroxyl Radicals,xe2x80x9d FEBS Letters, 128, 347-352, 1981.
Sutton, H. C., C. C. Winterboum, xe2x80x9cChelated Iron-catalyzed OH Formation from Paraquat Radicals and H2O2: Mechanism of Formate Oxidation,xe2x80x9d Arch. Biochem. Biophys. 235,106-115, 1984.
Graf, E., J. R. Mahoney, R. G. Bryant, J. W. Eaton, xe2x80x9cIron-catalyzed Hydroxyl Radical Formation.
Stringent Requirement for Free Iron Coordination Site,xe2x80x9d J. Biol. Chem. 259(6),3620-3624,1984.
Lindsey, M. E. and M. A. Tarr, xe2x80x9cInhibited Hydroxyl Radical Degradation of Aromatic Hydrocarbons in the Presence of Dissolved Fulvic Acid,xe2x80x9d Wat. Res. 34, 2385-2389, 2000.
Lindsey, M. E. and M. A. Tarr, Quantitation of Hydroxyl Radical During Fenton Oxidation Following a Single Addition of Iron And Peroxide,xe2x80x9d Chemosphere 41, 409-417, 2000.
The present invention is a method of oxidizing organic pollutants in a solution comprising chelating a catalytic metal with cyclodextrins (CD) and/or derivatized cyclodextrins (dCD), simultaneously complexing an organic pollutant with cyclodextrins (CD) and/or derivatized cyclodextrins (dCD). Preferably, hydrogen peroxide is added to the aqueous solution. Preferably, the metal catalyst is iron(II).
The use of the method of the present invention is anticipated to extend the range of applicability of Fenton remediation to a broader set of contaminants and soil systems than are currently possible. Furthermore, by improving the selectivity of the process for contaminants, the cost of raw materials will be decreased, providing more cost-effective remediation than currently available technologies. The successful implementation of this new technology would result in the following benefits:
A single method capable of removing hydrophobic pollutants from sorption sites in soil or sediment while at the same time degrading the pollutant in situ. Ultimately, the technique may be capable of complete in situ destruction of persistent, bioaccumulative, and toxic (PBT) pollutants with no residual waste material that would require additional treatment or disposal.
Cost-effective treatment and removal of PCBs, PAHs, DDT, and other PBT chemicals from contaminated sediments or soils.
An in-situ technology that mobilizes contaminants to make them more amenable to simultaneous or subsequent in situ or ex situ treatment.
In addition to hydrogen peroxide, sodium peroxide, calcium peroxide, or mixtures thereof may be applicable as reagents.
With respect to subsurface treatment, the three reagents, CD/dCD, iron salts, and peroxide(s) (hydrogen peroxide, sodium peroxide, calcium peroxide, or mixtures thereof) can be premixed and introduced into the subsurface or can be injected sequentially, simultaneously, or any combination thereof. The reagents may be introduced to the subsurface by any method considered conventional in the art. For example, vertical wells, horizontal wells, trenches or other techniques may be used. High pressure injection may be used, and current techniques of the art may be utilized to aid in delivery of the reagents to contaminated regions of the subsurface. Multiple applications of the reagents may be applied.
Determination of the optimum reagent mixture for subsurface application can be determined by performing tests on subsurface samples from the contaminated site. Samples collected from the site can be treated in the laboratory in sealed glass vessels to optimize the amount of each reagent and to determine the optimal order for adding reagents. Such studies may include optimization of the following parameters: 1) choice and amount of iron salt, 2) iron/cyclodextrin ratio, 3) pollutant/cyclodextrin ratio, 4) peroxide dose (of hydrogen peroxide, sodium peroxide, calcium peroxide, or mixtures thereof), 5) cyclodextrin type, 6) pre-equilibration of cyclodextrin-pollutant complex, 7) soil/water ratio, and 8) pH. Determination of pollutant concentrations before, during, and after treatment can be accomplished using appropriate EPA and/or NIST methods. Soil characterization may also be conducted, including analyses for iron content, pH, particle size, clay content, bulk density, and other relevant measurements.